1. Field of the Invention
The present invention relates to a silicon carbide semiconductor device having a Schottky junction and, more particularly, to a silicon carbide semiconductor device in which part of a Schottky electrode forming a Schottky junction is in contact with a terminal region such as a guard ring, and in which an outer peripheral end of the Schottky electrode is on an insulating film.
2. Background Art
Since a Schottky barrier diode (SBD) is a unipolar device, it is capable of reducing its switching loss compared with an ordinary bipolar diode. However, the withstand voltages of available practical SBDs having silicon as their constituent materials are about 50 V at the maximum. Therefore, SBDs having silicon as their constituent materials are not suitable for use in high-voltage inverters or the like. In contrast, SBDs having silicon carbide as their constituent materials and easily having a withstand voltage of about several kilovolts can be obtained. Applications to electric power conversion circuits of SBDs having silicon carbide as their constituent materials have therefore attracted attention in recent years.
As such an SBD having silicon carbide as its constituent material, a device such as described in Japanese Patent Laid-Open No. 2005-286197 (FIG. 1) for example is known. In the SBD disclosed in Japanese Patent Laid-Open No. 2005-286197 (FIG. 1), an overlay structure in which a Schottky electrode is extended over the outer peripheral end of a guard ring region is provided in order to extend a depletion layer produced around a PN junction between the guard ring region and an n-type semiconductor layer at the time of static application of a high voltage. Use of such a structure enables the depletion layer to extend easily in the n-type semiconductor layer, so that this SBD has high voltage blocking ability.